Viscosity in simple terms is the friction that a liquid experiences when it is flowing.
Atoms and molecules in a liquid are still bonded together. But, unlike in its solid states, the liquid is free to move as some of the bonds are weak or broken.
This is why liquids respond to gravity by flowing down a slope. They also take the shape of any container into which they are poured.
When layers of molecules are blocked from flowing past each other because of internal friction, the liquid is said to be viscous and it flows slowly.
When the internal friction is lower and the liquid is able to flow faster with lesser resistance, this liquid is a low-viscosity liquid.
The term viscosity comes from the Latin word Viscum meaning mistletoe. A sticky glue can be prepared from the mistletoe berries.
Viscosity is measured using Viscometers.
Oil has a higher viscosity that water but lesser viscosity than honey. Molasses, tar, and pitch have a higher viscosity than honey.
Honey has a higher viscosity and hence it flows slowly and it will not splash easily.
Oil has lesser viscosity than honey and it will flow easily but it will not splash much.
Water has low viscosity and it splashes easily when poured.
Factors that alter the stickiness of a liquid:
The viscosity of a liquid gets altered when its temperature is increased. For example, honey, when heated will flow faster than honey when it is at room temperature.
Pressure does not alter the viscosity of a liquid unless the pressure is very high.
Viscosity race with honey, oil, and water
This is a DIY fun experiment for kids that can be done at home.
In this experiment, three different liquids are made to race.
Keep a paper or cardboard at a gradient. Like any running race, mark the starting and ending points of the race.
Liquids can be poured one by one or at the same time to see which liquid takes the least time to reach the finish line.
Keep the gradient constant for all the liquids being tested.
The same amount of liquids has to be tested.
Liquids like syrup, corn syrup, molasses, ketchup, milk, and vinegar can be tested too.
Viscosity of lava
When lava is not viscous, it will flow easily. When lava is viscid, it will flow slowly which gives the outer surface enough time to cool down and form clumps. These clumps can block the flow of lava further slowing the flow. Volcanoes with highly viscous lava will erupt more violently because of the increased pressure caused by this blockage.